The invention relates to the balancing of integrally bladed rotors and in particular to the balancing of multi-disk rotors.
Bladed rotors such as compressors and turbines of gas turbine engines rotate at a high rate of speed. Dynamic unbalance of such rotors leads to severe vibration reducing the useful life of the component.
It is accordingly known to add or remove material at selected locations to achieve proper balance. Some schemes require machining operations on the disk itself, producing stress concentrations therein to the detriment of the rotor. Some require removal of the disks from the balancing machine for machining with later remounting on the balancing machine. This not only increases the labor involved but variations caused by remounting of the disk make the ultimate balancing difficult.
Copending application Ser. No. 94,213, entitled Rotor Balance System, filed on Sept. 8, 1987 by Novotny, describes a rotor balance system wherein a balance ring is shrunk fit within a bladed disk. Detail balancing of this subassembly is carried out by grinding only on the balance ring. This provides a lightweight ring with sufficient material to normally permit balancing of a disk. Integrally bladed disks, however, tend to have relatively high levels of initial unbalance. This unbalance can exceed or at least strain the balance capability of the described balance scheme. An approach to overcome the gross inital unbalance is therefore desirable.